1. Field of the Invention
Embodiments described herein relate generally to a charged particle beam pattern writing method and a charged particle beam writing apparatus and, for example, relates to a technique for writing a pattern by irradiating a target object above a stage with a beam.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor manufacturing processes. In recent years, with an increase in integration density of an LSI, a circuit linewidth required for semiconductor devices is getting smaller year by year. The electron beam pattern writing technology has inherently superior resolving power and is used to write a pattern to a wafer or the like by using an electron beam.
For example, a writing apparatus using multiple beams is known. When compared with a case in which a pattern is written using an electron beam, many beams can be irradiated at a time by using multiple beams and throughput can significantly be improved. In such a multi-beam writing apparatus, for example, a multi-beam is formed from an electron beam emitted from an electron gun assembly through a mask having a plurality of holes and each beam is blanking-controlled before a desired position on a target object being irradiated with each unshielded beam (see Japanese Patent Application Laid-Open No. 2006-261392, for example).
In an electron beam writing apparatus, a target object is placed above a stage and a pattern is written on the target object while moving the stage or performing a step and repeat operation. In this case, a pattern is written by focusing on the target object surface in the end while refracting a beam of each shot by an optical system such as an electromagnetic lens. However, even if focused by the optical system, a pattern cannot be written to a desired position if the stage position is displaced. This is, for example, a case when a rotational position displacement of the stage arises. Such a problem causes degradation in precision of the pattern writing position. In a single beam system, the number of beams is one and an X/Y directional displacement and a rotational displacement arise for one shot when a rotational position displacement of the stage arises and thus, a position error is in most cases not so great compared with a multi-beam system. In contrast to the single beam system, however, many beams are emitted simultaneously in one shot in the multi-beam system and thus, if a rotational position displacement of the stage arises, a rotational displacement arises in the whole multiple beams and a pattern writing position error could become intolerable. Thus, reducing such a rotational position displacement of the stage as much as possible is demanded. However, it is difficult to completely eliminate installation errors of the stage or rotational errors caused by a stage drive system. Such a problem is expected to grow while pattern writing precision is further sought in the future even in the single beam system.